Mechanical microstructures (MEMS) is a general term used to describe very small devices such as gears and levers, which may be combined to create complex, yet tiny machines. Such microstructures need not be limited to mechanical tools. For example, a tiny membrane can be employed as a sensor of differential gas pressures by measuring a capacitance between that membrane and an adjacent surface. Similarly, tiny cantilevers can be actuated via an applied electrical force to control valves for fluid flow. Other known microstructures include sharply pointed tips for microprobes used in atomic force microscopy or for field emitting structures.
As noted in an article by Gary Stix entitled, "Micron Machinations," Scientific American, November 1992, pp. 106-117, MEMS can differ from larger, more commonplace machines in structure, method of formation and method of use. Typically MEMS are fabricated with technologies developed for semiconductor processing, such as etching of silicon, because tools that are used for production of larger machines do not allow for the fine micromachining necessary to create MEMS. MEMS created from silicon or polysilicon substrates have characteristics derived from those materials. The substrates are hard, though brittle, and can be micromachined to create structures with submicron features. However, silicon and polysilicon are also fairly reactive, and if left exposed to air quickly form a silicon monoxide or dioxide surface layer which is weaker than the starting materials and which continues to grow into the substrate.
It is an object of the present invention to provide a method for making mechanical microstructures or portions thereof that are inert, durable, and harder than silicon and polysilicon.